evolved by the clashing of the atoms, and this amount was fixed and
definite. Thus to Joule we owe the foundation of chemical dynamics and
the basis of thermal chemistry. It was upon a knowledge of the mode of
arrangement of atoms, and on a recognition of their distinctive
properties, that the superstructure of modern organic chemistry
rested. We now assumed on good grounds that the atom of each element
possessed distinct capabilities of combination. The knowledge of the
mode in which the atoms in the molecule are arranged had given to
organic chemistry an impetus which had overcome many experimental
obstacles, and organic chemistry had now become synthetic.

Liebig and Wohler, in 1837, foresaw the artificial production in the
laboratories of all organic substances so far as they did not
constitute a living organism. And after fifty years their prophecy had
been fulfilled, for at the present time we could prepare an artificial
sweetening principle, an artificial alkaloid, and salacine.


SYNTHESIS.

We know now that the same laws regulate the formation of chemical
compounds in both animate and inanimate nature, and the chemist only
asked for a knowledge of the constitution of any definite chemical
compounds found in the organic world in order to be able to promise to
prepare it artificially. Seventeen years elapsed between Wohler's
discovery of the artificial production of urea and the next real
synthesis, which was accomplished by Kolbe, when in 1845 he prepared
acetic acid from its elements. Since then a splendid harvest of
results had been gathered in by chemists of all nations. In 1834 Dumas
made known the law of substitution, and showed that an exchange could